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See detailAngular correlation functions of X-ray point-like sources in the full exposure XMM-LSS field
Elyiv, Andrii ULg; Clerc, N.; Plionis, M. et al

in Astronomy and Astrophysics (2012), 537

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and ... [more ▼]

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and 2500 X-ray point-like sources over the 11 sq. deg. XMM-LSS field in the soft (0.5-2 keV) and hard (2-10 keV) bands. For the conversion from the angular to the spatial correlation function we used the Limber integral equation and the luminosity-dependent density evolution model of the AGN X-ray luminosity function. <BR /> Results: We have found significant angular correlations with the power-law parameters γ = 1.81 ± 0.02, θ[SUB]0[/SUB] = 1.3'' ± 0.2'' for the soft, and γ = 2.00 ± 0.04, θ[SUB]0[/SUB] = 7.3'' ± 1.0'' for the hard bands. The amplitude of the correlation function w(θ) is higher in the hard than in the soft band for f[SUB]x[/SUB] ≲ 10[SUP]-14[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] and lower above this flux limit. We confirm that the clustering strength θ[SUB]0[/SUB] grows with the flux limit of the sample, a trend which is also present in the amplitude of the spatial correlation function, but only for the soft band. In the hard band, it remains almost constant with r[SUB]0[/SUB] ≃ 10h[SUP]-1[/SUP] Mpc, irrespective of the flux limit. Our analysis of AGN subsamples with different hardness ratios shows that the sources with a hard-spectrum are more clustered than soft-spectrum ones. This result may be a hint that the two main types of AGN populate different environments. Finally, we find that our clustering results correspond to an X-ray selected AGN bias factor of 2.5 for the soft band sources (at a median <inline-formula>bar{z} ≃ 1.1) and 3.3 for the hard band sources (at a median <inline-formula>bar{z} ≃ 1), which translates into a host dark matter halo mass of 10[SUP]13[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] and 10[SUP]13.7[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] for the soft and hard bands, respectively. This paper is dedicated to the memory of Olivier Garcet who has initiated the present work just before his sudden death. [less ▲]

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See detailThe European Large-Area ISO Survey (ELAIS): the final band-merged catalogue
Rowan-Robinson, M.; Lari, C.; Perez-Fournon, I. et al

in Monthly Notices of the Royal Astronomical Society (2004), 351

We present the final band-merged European Large-Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 μm, and the associated data at U, g', r', i', Z, J, H, K and 20 cm. The origin of the survey ... [more ▼]

We present the final band-merged European Large-Area ISO Survey (ELAIS) Catalogue at 6.7, 15, 90 and 175 μm, and the associated data at U, g', r', i', Z, J, H, K and 20 cm. The origin of the survey, infrared and radio observations, data-reduction and optical identifications are briefly reviewed, and a summary of the area covered and the completeness limit for each infrared band is given. A detailed discussion of the band-merging and optical association strategy is given. The total Catalogue consists of 3762 sources. 23 per cent of the 15-μm sources and 75 per cent of the 6.7-μm sources are stars. For extragalactic sources observed in three or more infrared bands, colour-colour diagrams are presented and discussed in terms of the contributing infrared populations. Spectral energy distributions (SEDs) are shown for selected sources and compared with cirrus, M82 and Arp220 starburst, and active galactic nuclei (AGN) dust torus models. Spectroscopic redshifts are tabulated, where available. For the N1 and N2 areas, the Isaac Newton Telescope ugriz Wide Field Survey permits photometric redshifts to be estimated for galaxies and quasars. These agree well with the spectroscopic redshifts, within the uncertainty of the photometric method [~10 per cent in (1 +z) for galaxies]. The redshift distribution is given for selected ELAIS bands and colour-redshift diagrams are discussed. There is a high proportion of ultraluminous infrared galaxies (log[SUB]10[/SUB] of 1-1000 μm luminosity L[SUB]ir[/SUB] > 12.22) in the ELAIS Catalogue (14 per cent of 15-μm galaxies with known z), many with Arp220-like SEDs. 10 per cent of the 15-μm sources are genuine optically blank fields to r'= 24: these must have very high infrared-to-optical ratios and probably have z > 0.6, so are high-luminosity dusty starbursts or Type 2 AGN. Nine hyperluminous infrared galaxies (L[SUB]ir[/SUB] > 13.22) and nine extremely red objects (EROs) (r-K > 6) are found in the survey. The latter are interpreted as ultraluminous dusty infrared galaxies at z~ 1. The large numbers of ultraluminous galaxies imply very strong evolution in the star formation rate between z= 0 and 1. There is also a surprisingly large population of luminous (L[SUB]ir[/SUB] > 11.5), cool (cirrus-type SEDs) galaxies, with L[SUB]ir[/SUB]-L[SUB]opt[/SUB] > 0, implying A[SUB]V[/SUB] > 1. [less ▲]

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